lecture recording on 28 January 2025 at 12.04.41 PM

Introduction to VO2 and Performance

• VO2 refers to the absolute amount of oxygen required for an activity, measured in milliliters per minute.

• VO2 max is also an absolute value representing the maximum amount of oxygen one can consume during intense exercise, also measured in milliliters per minute.

• It’s essential to distinguish between absolute values (like VO2 and VO2 max) and relative values, which are often communicated as a percentage of VO2 max.

Relative vs. Absolute Values

• Relative VO2: Represents the intensity based on a percentage of VO2 max.

  • Example: If a person has a VO2 max of 100 ml/min and is utilizing 50 ml/min for an activity, they are working at 50% of their VO2 max.

• Most physiological adaptations and responses correlate more closely with the percentage of VO2 max rather than with absolute VO2 values.

• Adaptations typically occur when the intensity reaches around 70% of VO2 max.

Measuring Oxygen Uptake

• During exercise, oxygen uptake increases with intensity and typically plateaus when VO2 max is reached despite continued exercise.

• Decreasing the treadmill speed does not change VO2 max but alters the rate of reaching maximum oxygen uptake.

Effects of Training on VO2 Max

• Training programs enhance VO2 max by improving one’s ability to consume oxygen.

• Training induces physiological changes, resulting in higher maximum oxygen uptake after several weeks of consistent exercise.

• Individuals still experience fatigue after reaching VO2 max, but trained individuals will have a greater capacity to endure longer or harder intensities before fatigue.

Physiological Implications of Absolute and Relative Values

• Absolute values of VO2 and VO2 max are important for comparing performance over time (e.g., progress in a training program).

• Relative values allow for comparisons between individuals or animals, such as two horses with different VO2 max values yet same mechanical efficiency.

  • Example: One horse's performance at 80 ml/min (relative to their 160 ml/min VO2 max) equates to 50%, while another at 80 ml/min relative to a 115 ml/min VO2 max is at about 70%.

  • Conclusion: The horse working at a higher percentage (70%) will likely fatigue faster than one working at 50%.

Oxygen Deficit and Oxygen Debt

• Oxygen Deficit: Occurs at the beginning of exercise when oxygen demand exceeds supply, often relying on anaerobic metabolism.

• This period is characterized by insufficient oxygen consumption for ATP production, creating an energy deficit.

• Oxygen Debt (EPOC): Refers to the increased oxygen consumption during recovery post-exercise, surpassing the initial deficit.

• The debt consists of two phases:

  • Fast Phase (Alactic): Recovery involving regeneration of high-energy phosphates (ATP and phosphocreatine).

  • Slow Phase: Involves tissue repair, lactate metabolism, and additional recovery processes.

Conclusion

• In summary, understanding the interplay between VO2, VO2 max, and the concepts of oxygen deficit and debt is crucial for analyzing performance and training effectiveness in both human and animal subjects. The physiological adaptations and responses are largely influenced by the intensity of exercise relative to one's VO2 max.